In German patent specification No. 21 64 058 and related Vogelsang U.S. Pat. No. 3,813,384 (the entire disclosure of which is hereby incorporated by reference and relied upon) there are disclosed basic substituted 4-benzyl-1-(2H)-phthalazinone derivatives of the following formula ##STR2## wherein R represents hydrogen or a halogen atom, a trifluoromethyl group or a lower alkyl or alkoxy group and E represents a 4-perhydroazepinyl, N-methyl-4-perhydroazepinyl, 3-quinuclidinyl, 3-tropanyl, 3-nortropanyl, N-methyl-3-pyrrolidinyl or N-methyl-2-pyrrolidinyl-methyl radical as well as physiologically acceptable acid addition salts thereof.
These compounds possess antihistamine activity.